Uniformly 14 C-labelled plant cell walls: Production, analysis and behaviour in rat gastrointestinal tract

Abstract

Uniformly 14 C-labelled primary cell walls ( 14 C-PCW) were purified from suspension-cultured cells of spinach ( Spinacia oleracea L.) grown in a medium containing D-[U- 14 C]glucose. The approximate polymer composition of the 14 C-PCW preparation (% total 14 C) was homogalacturonan 30,rhamnogalacturonan 23, xyloglucan 10, other hemicelluloses 3, cellulose 21, lignin 0, 14 C-labelled protein < 3 and [ 14 C]starch < 2. The degree of methyl esterification of the pectic polysaccharides was about 25%. The 14 C-PCW contained about 4% O -acetyl and 3% non-volatile ester-linked residues. When tracer levels of these 14 C-PCW were fed to rats, only about 18% of the 14 C appeared in the faeces;negligible levels of 14 C (0.07%) remained in the gut contents 4 d after feeding. Some 14 C was present in the carcass. The results show that U- 14 C-labelled primary cell walls can be purified and radiochemically analysed by the methods developed here, and that primary cell walls are extensively fermented by the gut microflora of the rat.